%%% id_server.erl - a server to manage ids for programme uris
%%%
%%% The MIT License
%%%
%%% Copyright (c) 2008 hellomatty@gmail.com
%%%
%%% Permission is hereby granted, free of charge, to any person obtaining a copy
%%% of this software and associated documentation files (the "Software"), to deal
%%% in the Software without restriction, including without limitation the rights
%%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
%%% copies of the Software, and to permit persons to whom the Software is
%%% furnished to do so, subject to the following conditions:
%%%
%%% The above copyright notice and this permission notice shall be included in
%%% all copies or substantial portions of the Software.
%%%
%%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
%%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
%%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
%%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
%%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
%%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
%%% THE SOFTWARE.
%%%

-module(id_server).

-include_lib("util.hrl").

-behaviour(gen_server). 

-export([start_link/0]). 
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, 
terminate/2, code_change/3]). 

start_link() -> gen_server:start_link({local, ?MODULE}, ?MODULE, [], []). 

-record(state, {
}).

init([]) ->
  prepare(id_uri),
  prepare(sequence),
  {ok, #state{}}. 

handle_call({id, Uri}, _From, State) ->
  {reply, id_for_uri(Uri), State};
handle_call({ids, Uris}, _From, State) ->
  {reply, lists:map(fun(Uri) -> id_for_uri(Uri) end, Uris), State}.

handle_cast(_Msg, State) -> {noreply, State}. 

handle_info(_Info, State) -> {noreply, State}. 

terminate(_Reason, _State) -> ok. 

code_change(_OldVsn, State, _Extra) -> {ok, State}. 

id_for_uri(Uri) ->
  case ets:lookup(id_uri, Uri) of
    [] ->
      NextId = try
        ets:update_counter(sequence, id_uri, 1)
      catch
        _:_ ->
          InitialId = 1000,
          ets:insert(sequence, {id_uri, InitialId}),
          InitialId
      end,
      ets:insert(id_uri, {Uri, NextId}),
      ets:insert(id_uri, {NextId, Uri}),
      NextId;
    [{_Uri, Id}] ->
      Id
  end.

prepare(Table) ->
  case lists:member(Table, ets:all()) of
    false ->
      ?D({prepare,create,Table}),
      ets:new(Table, [protected, set, named_table]);
    true ->
      ok
  end.
